Field of the Invention
The present invention relates to a fixing device and an image forming device.
Description of the Related Art
An image forming device provided with an image forming unit which allows toner to adhere to paper to form an image and an image fixing unit which heats and pressurizes the paper to which the toner is adhered to fix the toner on the paper is conventionally known. There is the image fixing unit which heats and pressurizes the paper by means of a nip portion of a roller pair including a heating roller in which a heater is embedded and that which heats and pressurizes the paper through a fixing belt stretched on the above-described heating roller.
A heater capable of generating large inrush current such as a halogen heater is generally used as the heater of the heating roller. Therefore, a flicker beyond a predetermined standard value might occur due to fluctuation in power supply voltage caused by the inrush current when the power consumption drastically changes such as when energization of the heater is started in the above-described image forming device. In view of this, JP 2001-343858 A discloses the technology of inhibiting the occurrence of the flicker by decreasing a change amount when the power consumption of the heater changes by performing half-wave control of stepping up a duty ratio of a period in which the heater is energized in units of half cycle of a voltage waveform of an AC power supply.
However, when rated power of the heater is large, the change amount when the power consumption changes does not become sufficiently small by control of an energizing period in units of half cycle of the voltage waveform of the AC power supply and the flicker beyond the standard value problematically occurs.
When the power consumption of the heater is slightly stepped up by phase control in place of the half-wave control in order to inhibit the flicker, there is a problem that it takes time for the heating roller (fixing unit) to be heated to desired temperature.